On a vehicle such as an automobile, usually, a relay for controlling connections between a power supply apparatus and loads (a battery assembly and an electric motor constitute an example of the relationships) is mounted. In an electric vehicle which travels by using an electric motor, a hybrid vehicle which travels by using both an engine and an electric motor, or the like, for example, a relay supplies an electric power to the electric motor through an inverter. The relay includes a main relay which connects and disconnects the output of a battery assembly that is to be supplied to the inverter. The main relay has a pair of relay terminals. One of the relay terminals is connected to the integrated positive electrode of the battery assembly through a circuit, and the other relay terminal is connected to the integrated negative electrode of the battery assembly through a circuit.
The relay is one of components of a junction box which is disposed between the battery assembly and the electric motor, and fixed to the housing of the junction box (see Patent Literature 1). In the configuration disclosed in Patent Literature 1, first regulating portions which regulate the horizontal movement of the relay, and second regulating portions which regulate the vertical movement are disposed in the housing. In the relay, a flange is formed over the entire circumference of the lower portion. According to the configuration, then the relay is to be fixed to the housing, the lower surface of the flange abuts against the first regulating portions, and the horizontal movement along the fixing surface is regulated. In this case, the flange abuts against engaging pieces formed on the second regulating portions to press tip end portions of the engaging pieces, thereby causing the engaging pieces to be elastically flexurally deformed. When the lower surface of the flange then abuts against the first regulating portions, the engaging pieces are elastically flexurally return deformed, and the tip end portions are engaged with the upper surface of the flange. As a result, the movement of the relay which is perpendicular to the fixing surface is regulated.